Footwear with a sole structure incorporating a lobed fluid-filled chamber

ABSTRACT

A fluid-filled chamber for an article of footwear and a method for manufacturing the chamber are disclosed. The chamber may be incorporated into a sole structure of the footwear and includes a central area and a plurality of lobes extending outward from the central area. The lobes are in fluid communication with the central area and are formed from a first surface, a second surface, and a sidewall. The sidewall joins with the first surface with the second surface to seal the fluid within the chamber, but no internal connections are generally utilized to join interior portions of the first surface with interior portions of the second surface. The fluid within the chamber may be air at a pressure that is approximately equal to an ambient pressure.

CROSS-REFERENCE TO RELATED APPLICATION

This U.S. Patent Application is a continuation-in-part application ofand claims priority to U.S. patent application Ser. No. 10/620,843,which was filed in the U.S. Patent and Trademark Office on Jul. 16, 2003and entitled Footwear With A Sole Structure Incorporating A LobedFluid-Filled Chamber, such prior U.S. Patent Application being entirelyincorporated herein by reference.

BACKGROUND OF THE INVENTION

A conventional article of footwear includes two primary elements, anupper and a sole structure. With respect to athletic footwear, forexample, the upper generally includes multiple material layers, such astextiles, foam, and leather, that are stitched or adhesively bondedtogether to form a void on the interior of the footwear for securely andcomfortably receiving a foot. The sole structure has a layeredconfiguration that includes an insole, a midsole, and an outsole. Theinsole is a thin cushioning member positioned within the void andadjacent the foot to enhance footwear comfort. The midsole forms amiddle layer of the sole structure and is often formed of a foammaterial, such as polyurethane or ethylvinylacetate. The outsole issecured to a lower surface of the midsole and provides a durable,wear-resistant surface for engaging the ground.

Midsoles formed of conventional foam materials compress resilientlyunder an applied load, thereby attenuating forces and absorbing energyassociated with walking or running, for example. The resilientcompression of the foam materials is due, in part, to the inclusion ofcells within the foam structure that define an inner volumesubstantially displaced by gas. That is, the foam materials include aplurality of pockets that enclose air. After repeated compressions,however, the cell structures may begin to permanently collapse, whichresults in decreased compressibility of the foam. Accordingly, theoverall ability of the midsole to attenuate forces and absorb energydeteriorates over the life of the midsole.

One manner of minimizing the effects of the cell structure collapse inconventional foam materials involves the use of a structure having theconfiguration of a fluid-filled chamber, as disclosed in U.S. Pat. No.4,183,156 to Rudy, hereby incorporated by reference. The fluid-filledchamber has the structure of a bladder that includes an outer enclosingmember formed of an elastomeric material that defines a plurality oftubular members extending longitudinally throughout the length of anarticle of footwear. The tubular members are in fluid communication witheach other and jointly extend across the width of the footwear. U.S.Pat. No. 4,219,945 to Rudy, also incorporated by reference, discloses asimilar fluid-filled chamber encapsulated in a foam material, whereinthe combination of the fluid-filled chamber and the encapsulating foammaterial functions as a midsole.

U.S. Pat. No. 4,817,304 to Parker, et al., hereby incorporated byreference, discloses a foam-encapsulated, fluid-filled chamber in whichapertures are formed in the foam and along side portions of the chamber.When the midsole is compressed, the chamber expands into the apertures.Accordingly, the apertures provide decreased stiffness duringcompression of the midsole, while reducing the overall weight of thefootwear. Further, by appropriately locating the apertures in the foammaterial, the overall impact response characteristics may be adjusted inspecific areas of the footwear.

The fluid-filled chambers described above may be manufactured by atwo-film technique, wherein two separate layers of elastomeric film areformed to have the overall shape of the chamber. The layers are thenwelded together along their respective peripheries to form an uppersurface, a lower surface, and sidewalls of the chamber, and the layersare welded together at predetermined interior locations to impart adesired configuration to the chamber. That is, interior portions of thelayers are connected to form chambers of a predetermined shape and sizeat desired locations. The chambers are subsequently pressurized aboveambient pressure by inserting a nozzle or needle, which is connected toa fluid pressure source, into a fill inlet formed in the chamber. Afterthe chambers are pressurized, the nozzle is removed and the fill inletis sealed, by welding for example.

Another manufacturing technique for manufacturing fluid-filled chambersof the type described above is through a blow-molding process, wherein aliquefied elastomeric material is placed in a mold having the desiredoverall shape and configuration of the chamber. The mold has an openingat one location through which pressurized air is provided. Thepressurized air forces the liquefied elastomeric material against theinner surfaces of the mold and causes the material to harden in themold, thereby forming the chamber to have the desired configuration.

Another type of chamber utilized in footwear midsoles is disclosed inU.S. Pat. Nos. 4,906,502 and 5,083,361, both to Rudy, and both herebyincorporated by reference. The chambers comprise a hermetically sealedouter barrier layer that is securely bonded over a double-walled fabriccore. The double-walled fabric core has upper and lower outer fabriclayers normally spaced apart from each another at a predetermineddistance, and may be manufactured through a double needle bar Raschelknitting process. Connecting yarns, potentially in the form ofmulti-filament yarns with many individual fibers, extend internallybetween the facing surfaces of the fabric layers and are anchored to thefabric layers. The individual filaments of the connecting yarns formtensile restraining members that limit outward movement of the barrierlayers to a desired distance.

U.S. Pat. Nos. 5,993,585 and 6,119,371, both issued to Goodwin et al.,and both hereby incorporated by reference, also disclose chambersincorporating a double-walled fabric core, but without a peripheral seamlocated midway between the upper and lower surfaces of the chamber.Instead, the seam is located adjacent to the upper surface of thechamber. Advantages in this design include removal of the seam from thearea of maximum sidewall flexing and increased visibility of theinterior of the chamber, including the connecting yarns. The processused to manufacture a chamber of this type, involves the formation of ashell, which includes a lower surface and a sidewall, with a mold. Thedouble-walled fabric core is placed on top of a covering layer, and theshell is placed over the covering layer and core. The assembled shell,covering layer, and core are then moved to a lamination station whereradio frequency energy bonds opposite sides of the core to the shell andcovering layer, and bonds a periphery of the shell to the coveringlayer. The chamber is then pressurized by inserting a fluid so as toplace the connecting yarns in tension.

A process for thermoforming a chamber is disclosed in U.S. Pat. No.5,976,451 to Skaja et al., hereby incorporated by reference, wherein apair of flexible thermoplastic resin layers are heated and placedagainst a pair of molds, with a vacuum drawing the layers into the mold.The layers are then pressed together to form the chamber.

The material forming outer layers of the chambers discussed above may beformed of a polymer material, such as a thermoplastic elastomer, that issubstantially impermeable to the fluid within the chamber. Morespecifically, one suitable material is a film formed of alternatinglayers of thermoplastic polyurethane and ethylene-vinyl alcoholcopolymer, as disclosed in U.S. Pat. Nos. 5,713,141 and 5,952,065 toMitchell et al, hereby incorporated by reference. A variation upon thismaterial wherein the center layer is formed of ethylene-vinyl alcoholcopolymer; the two layers adjacent to the center layer are formed ofthermoplastic polyurethane; and the outer layers are formed of a regrindmaterial of thermoplastic polyurethane and ethylene-vinyl alcoholcopolymer may also be utilized. Another suitable material is a flexiblemicrolayer membrane that includes alternating layers of a gas barriermaterial and an elastomeric material, as disclosed in U.S. Pat. Nos.6,082,025 and 6,127,026 to Bonk et al., both hereby incorporated byreference. Other suitable thermoplastic elastomer materials or filmsinclude polyurethane, polyester, polyester polyurethane, polyetherpolyurethane, such as cast or extruded ester-based polyurethane film.Additional suitable materials are disclosed in the '156 and '945 patentsto Rudy, which were discussed above. In addition, numerous thermoplasticurethanes may be utilized, such as PELLETHANE, a product of the DowChemical Company; ELASTOLLAN, a product of the BASF Corporation; andESTANE, a product of the B.F. Goodrich Company, all of which are eitherester or ether based. Still other thermoplastic urethanes based onpolyesters, polyethers, polycaprolactone, and polycarbonate macrogelsmay be employed, and various nitrogen blocking materials may also beutilized. Further suitable materials include thermoplastic filmscontaining a crystalline material, as disclosed in U.S. Pat. Nos.4,936,029 and 5,042,176 to Rudy, hereby incorporated by reference, andpolyurethane including a polyester polyol, as disclosed in U.S. Pat.Nos. 6,013,340; 6,203,868; and 6,321,465 to Bonk et al., also herebyincorporated by reference.

The fluid contained within the chamber may include any of the gassesdisclosed in U.S. Pat. No. 4,340,626 to Rudy, such as hexafluoroethaneand sulfur hexafluoride, for example. In addition, some chambers enclosepressurized nitrogen gas or air.

SUMMARY OF THE INVENTION

The present invention is a chamber for an article of footwear thatincludes a first surface, an opposite second surface, and a sidewallextending between edges of the first surface and the second surface. Thesidewall is joined with the first surface and the second surface suchthat no internal connections secure interior portions of the firstsurface to interior portions of the second surface. A fluid is sealedwithin the chamber at a pressure between an ambient pressure and fivepounds per square inch of the ambient pressure. Furthermore, a pluralityof lobes extend outward from a central area of the chamber. The lobesare defined by the first surface, second surface, and sidewall, and thelobes are in fluid communication with the central area.

The first surface and the second surface may have a planarconfiguration. Alternately, one of the surfaces may be curved. Inaddition, portions of the sidewall positioned between the lobes may havea sloped configuration, and the portions of the sidewall adjacent distalends of the lobes may have a substantially vertical slope.

The lobes may be configured to extend radially outward from the centralarea. Accordingly, the lobes may extend outward in different directionsfrom the periphery of the central area. The number of lobes may varysignificantly within the scope of the invention. The lobes define spaceslocated between adjacent lobes. When incorporated into an article offootwear, the chamber will be at least partially encapsulated within apolymer foam material. Accordingly, the polymer foam will extend betweenthe lobes to form columns. In general, the surface of the columns willcontact the sidewall and have the shape of the spaces between theadjacent lobes. Accordingly, the columns will have a slopedconfiguration that corresponds with the sidewall slope.

The material that forms the chamber will generally be a polymer, such asa thermoplastic elastomer, thereby providing the structure of a bladder.Alternately, the chamber may be formed as a void within a midsole of thefootwear. Although a plurality of fluids may be utilized within thechamber, air generally provides properties that are suitable for theinvention.

The invention also relates to a method of manufacturing a fluid-filledchamber for an article of footwear. The method involves positioning aparison between a first portion and a corresponding second portion of amold. The parison is then bent with contours of the mold as the firstportion and the second portion translate toward each other, the contoursof the mold being positioned separate from a cavity within the mold, thecavity having a shape of the chamber. Opposite sides of the parison arethen shaped to form the chamber within the cavity, and the oppositesides of the parison are bonded together.

The advantages and features of novelty characterizing the presentinvention are pointed out with particularity in the appended claims. Togain an improved understanding of the advantages and features ofnovelty, however, reference may be made to the following descriptivematter and accompanying drawings that describe and illustrate variousembodiments and concepts related to the invention.

DESCRIPTION OF THE DRAWINGS

The foregoing Summary of the Invention, as well as the followingDetailed Description of the Invention, will be better understood whenread in conjunction with the accompanying drawings.

FIG. 1 is a side elevational view of an article of footwear having amidsole that incorporates a first chamber in accordance with the presentinvention.

FIG. 2 is a perspective view of the midsole depicted in FIG. 1.

FIG. 3 is a exploded perspective view of the midsole depicted in FIG. 1.

FIG. 4 is a perspective view of the first chamber.

FIG. 5 is another perspective view of the first chamber.

FIG. 6A is a top plan view of the first chamber.

FIG. 6B is a cross-section of the first chamber, as defined by line6B-6B in FIG. 6A.

FIG. 6C is another cross-section of the first chamber, as defined byline 6C-6C in FIG. 6A.

FIG. 6D is yet another cross-section of the first chamber, as defined byline 6D-6D in FIG. 6A.

FIG. 7 is a bottom plan view of the first chamber.

FIG. 8 is a side elevational view of another article of footwear havinga midsole that incorporates a second chamber in accordance with thepresent invention.

FIG. 9 is a perspective view of the midsole depicted in FIG. 8.

FIG. 10 is an exploded perspective view of the midsole depicted in FIG.8.

FIG. 11 is a perspective view of the second chamber.

FIG. 12 is another perspective view of the second chamber.

FIG. 13A is a top plan view of the second chamber.

FIG. 13B is a cross-section of the second chamber, as defined by line13B-13B in FIG. 13A.

FIG. 13C is another cross-section of the second chamber, as defined byline 13C-13C in FIG. 13A.

FIG. 13D is yet another cross-section of the second chamber, as definedby line 13D-13D in FIG. 13A.

FIG. 14 is a bottom plan view of the second chamber.

FIG. 15 is an elevational view of the second chamber.

FIG. 16 is a perspective view of a mold for forming the second chamber.

FIG. 17 is a plan view of a first portion of the mold.

FIG. 18 is a plan view of a second portion of the mold.

FIG. 19 is a side elevational view of a parison positioned between thefirst and second portions of the mold prior to molding.

FIG. 20 is a side elevational view of the parison positioned between thefirst and second portions of the mold during an intermediate portion ofmolding.

FIG. 21 is a side elevational view of the parison positioned between thefirst and second portions of the mold during another intermediateportion of molding.

FIG. 22 is a side elevational view of a parison positioned between thefirst and second portions of the mold following molding.

FIG. 23 is a first perspective view of the second chamber formed in theparison.

FIG. 24 is a second perspective view of the second chamber formed in theparison.

FIG. 25 is a perspective view of the second chamber that highlights aposition of a parting line.

FIGS. 26 and 27 are side elevational views of another configuration ofthe footwear depicted in FIG. 8, wherein the midsole incorporates athird chamber in accordance with the present invention.

FIG. 28 is a perspective view of the third chamber.

FIG. 29 is another perspective view of the third chamber.

FIG. 30 is a top plan view of the third chamber.

FIG. 31 is a bottom plan view of the third chamber.

FIGS. 32 and 33 are elevational views of the third chamber.

FIG. 34 is a top plan view of another configuration of the thirdchamber.

DETAILED DESCRIPTION OF THE INVENTION

Introduction

The following discussion and accompanying figures disclose articles ofathletic footwear incorporating fluid-filled chambers in accordance withthe present invention. Concepts related to the footwear, and moreparticularly the fluid-filled chambers, are disclosed with reference tofootwear having a configuration that is suitable for running. Theinvention is not solely limited to footwear designed for running,however, and may be applied to a wide range of athletic footwear styles,including basketball shoes, cross-training shoes, walking shoes, tennisshoes, soccer shoes, and hiking boots, for example. In addition, theinvention may also be applied to non-athletic footwear styles, includingdress shoes, loafers, sandals, and work boots. Accordingly, one skilledin the relevant art will appreciate that the concepts disclosed hereinapply to a wide variety of footwear styles, in addition to the specificstyle discussed in the following material and depicted in theaccompanying figures.

First Chamber

An article of footwear 10 is depicted in FIG. 1 and includes an upper 20and a sole structure 30. Upper 20 has a substantially conventionalconfiguration and includes a plurality elements, such as textiles, foam,and leather materials, that are stitched or adhesively bonded togetherto form an interior void for securely and comfortably receiving thefoot. Sole structure 30 is positioned below upper 20 and includes twoprimary elements, a midsole 31 and an outsole 32. Midsole 31 is securedto a lower surface of upper 20, through stitching or adhesive bondingfor example, and operates to attenuate forces and absorb energy as solestructure 30 contacts the ground. That is, midsole 31 is structured toprovide the foot with cushioning during walking or running, for example.Outsole 32 is secured to a lower surface of midsole 31 and is formed ofa durable, wear-resistant material that engages the ground. In addition,sole structure 30 may include an insole, which is a thin cushioningmember, located within the void and adjacent to the foot to enhance thecomfort of footwear 10.

Midsole 31 is primarily formed of a polymer foam material, such aspolyurethane or ethylvinylacetate, that encapsulates a fluid-filledchamber 40. As depicted in FIGS. 2 and 3, chamber 40 is positioned in aheel region of midsole 31, which corresponds with the area of highestinitial load during footstrike. Chamber 40 may, however, be positionedin any region of midsole 31 to obtain a desired degree of cushioningresponse. Furthermore, midsole 31 may include multiple fluid-filledchambers having the general configuration of chamber 40.

Chamber 40 is depicted as having the structure of a bladder, whereinsealed layers of polymeric material enclose a fluid. Alternately,chamber 40 may be formed as a void within midsole 31. That is, materialhaving the shape of chamber 40 may be absent from midsole 31, therebyforming chamber 40.

In comparison with chambers of the prior art, chamber 40 and itsarrangement in the foam material of midsole 31 produces a relativelylarge deflection for a given load during initial stages of compression.As the compression of chamber 40 increases, however, the stiffness ofchamber 40 increases in a corresponding manner. This response tocompression, which will be described in greater detail in the followingmaterial, is due to the structure of chamber 40 and the manner in whichchamber 40 is incorporated into midsole 31. In general, the structure ofchamber 40 may be characterized as a single chamber, fluid-filledbladder. More particularly, chamber 40 has a central area 41 surroundedby five lobes 42 a-42 e that each have a distal end 43 a-43 e,respectively, as depicted in FIGS. 4-7. Lobes 42 a-42 e extend radiallyoutward from central area 41. Accordingly, lobes 42 a-42 e may extendoutward in different directions from a periphery of central area 41. Incombination with the foam material of midsole 31, which fills the spacesbetween lobes 42 a-42 e, midsole 31 provides an appropriate ratio of airto foam in specific areas under the heel of the foot.

For purposes of reference, a longitudinal axis 44 is depicted in FIGS.6A and 7 as extending through central area 41 and lobe 42 c. Chamber 40is symmetrical about a plane that extends through axis 44 and isgenerally perpendicular to the plane of FIGS. 6A and 7, while otherwisebeing asymmetrical. Accordingly, the structure of chamber 40 generallyresembles the shape of an oak leaf. Chamber 40 also includes a firstsurface 45, an opposite second surface 46, and a sidewall 47 thatextends between first surfaces 45 and 46. Both first surface 45 andsecond surface 46 have a generally planar configuration and areuniformly spaced apart from each other. First surface 45 has the generalshape of second surface 46, but with a reduced area. Accordingly,sidewall 47 slopes in the area between the individual lobes 42 a-42 e.For example, the slope of sidewall 47 may be approximately 40 degreesadjacent to central area 41, approximately 80 degrees adjacent to distalends 43 a-43 e, and gradually changing from 40 degrees to 80 degrees inthe area between. At the position of distal ends 43 a-43 e, however,sidewall 47 has a substantially vertical slope of 90 degrees. Sidewall47 may have a substantially planar configuration that forms an anglewith respect to first surface 45, or sidewall 47 may be curved.

The specific configuration of midsole 31 and the orientation of chamber40 may vary within the scope of the invention. When encapsulated by thepolymer foam material in midsole 31, for example, a portion of distalends 43 a-43 e may extend to an edge 33 of midsole 31, and may extendthrough edge 33 such that they are visible from the exterior of footwear10. Furthermore, first surface 45 may be coextensive with the plane ofthe upper surface of midsole 31 such that the heel engages first surface45. Alternately, chamber 40 may be entirely embedded within the foammaterial of midsole 31, or may be positioned with second surface 46being coextensive with the plane of the upper surface of midsole 31. Asdepicted in FIGS. 1-3, however, distal ends 43 a-43 e do not extendthrough edge 33 and second surface 46 is positioned adjacent a lowersurface of midsole 31. This configuration places a portion of the foammaterial in midsole 31 between the foot and first surface 45.

The slope of sidewall 47, which is depicted in the cross-sectional viewsof FIGS. 6B-6D, varies around chamber 40 to provide a smooth transitionfrom chamber 40 to the polymer foam material of midsole 31 duringcompression. As discussed above, sidewall 47 slopes from approximately40 degrees to 80 degrees between adjacent lobes 42 a-42 e and has asubstantially vertical slope at distal ends 43 a-43 e. The spacesbetween adjacent lobes 42 a-42 e have a generally U-shaped configurationin plan view, which is created by a curved surface of sidewall 47. Theportion of sidewall 47 positioned between adjacent lobes 42 a-42 e has aslope that is greater in areas adjacent to distal ends 43 a-43 e than inareas adjacent to central area 41. More specifically, sidewall 47 has arelatively shallow slope adjacent to central area 41, which correspondswith the rounded portion of the U-shaped configuration. As sidewall 47extends between central area 41 and distal ends 43 a-43 e, the slopeincreases. At distal ends 43 a-43 e, however, the slope of sidewall 47is substantially vertical. In other embodiments of the presentinvention, however, the slope of sidewall 47 may differ from thespecific configuration discussed herein to provide different degrees oftransition during compression.

The slopes of sidewall 47 between the various lobes 42 a-42 e areinversely matched by the resilient foam material of midsole 31.Accordingly, midsole 31 has a configuration with a plurality of columns34 that are formed of the foam material and extend between lobes 42 a-42e to contact the various areas of sidewall 47. The height of each column34 increases from positions adjacent to first surface 45 to positionsadjacent to second surface 46, and each column 34 slopes in a mannerthat corresponds with sidewall 47. Furthermore, due to the increasingspacing between lobes 42 a-42 e as they extend radially outward fromcentral area 42, the width of each column 43 increases accordingly.

A variety of materials may be utilized to form first surface 45, secondsurface 46, and sidewall 47, including the polymeric materials that areconventionally utilized in forming the outer layers of fluid-filledchambers for footwear, as discussed in the Background of the Inventionsection. In contrast with a majority of the prior art chamberstructures, however, the fluid within chamber 40 is at ambient pressureor at a pressure that is slightly elevated from ambient. Accordingly,the pressure of the fluid within chamber 40 may range from a gaugepressure of zero to over five pounds per square inch. Due to therelatively low pressure within chamber 40, the materials utilized toform first surface 45, second surface 46, and sidewall 47 need notprovide the barrier characteristics that operate to retain therelatively high fluid pressures of prior art chambers. Accordingly, awide range of polymeric materials such as thermoplastic urethane may beutilized to form first surface 45, second surface 46, and sidewall 47,and a variety of fluids such as air may be utilized within chamber 40.Furthermore, the wide range of polymeric materials may be selected basedupon the engineering properties of the material, such as the dynamicmodulus and loss tangent, rather than the ability of the material toprevent the diffusion of the fluid contained by chamber 40. When formedof thermoplastic polyurethane, first surface 45, second surface 46, andsidewall 47 may have a thickness of approximately 0.040 inches, but thethickness may range, for example, from 0.018 inches to 0.060 inches.

The relatively low pressure of the fluid within chamber 40 also providesanother difference between chamber 40 and prior art chambers. Therelatively high pressure in prior art chambers often requires theformation of internal connections between the polymer layers to preventthe chamber from expanding outward to a significant degree. That is,internal connections were utilized in prior art chambers to controloverall thickness of the chambers. In contrast, chamber 40 does not haveinternal connections between first surface 45 and second surface 46.

Chamber 40 may be manufactured through a variety of manufacturingtechniques, including blow-molding, thermoforming, and rotationalmolding, for example. With regard to the blow-molding technique,thermoplastic material is placed in a mold having the general shape ofchamber 40 and pressurized air is utilized to induce the material tocoat surfaces of the mold. In the thermoforming technique, layers ofthermoplastic material are placed between corresponding portions of amold, and the mold is utilized to compress the layers together atperipheral locations of chamber 40. A positive pressure may be appliedbetween the layers of thermoplastic material to induce the layers intothe contours of the mold. In addition, a vacuum may be induced in thearea between the layers and the mold to draw the layers into thecontours of the mold.

Chamber 40 and its arrangement in the foam material of midsole 31produces a relatively large deflection for a given load during initialstages of compression when compared to the fluid-filled chambersdiscussed in the Background of the Invention section. As the compressionof chamber 40 increases, however, the stiffness of chamber 40 increasesin a corresponding manner due to the structure of chamber 40 and themanner in which chamber 40 is incorporated into midsole 31. Threephenomena operate simultaneously to produce the effect described aboveand include pressure ramping, the properties of the foam material inmidsole 31, and film tensioning. Each of these phenomena will bedescribed in greater detail below.

Pressure ramping is the increase in pressure within chamber 40 thatoccurs as a result of compressing chamber 40. In effect, chamber 40 hasan initial pressure and initial volume when not being compressed withinmidsole 31. As midsole 31 is compressed, however, the effective volumeof chamber 40 decreases, thereby increasing the pressure of the fluidwithin chamber 40. The increase in pressure operates to provide aportion of the cushioning response of midsole 31.

The properties of the foam material also affect the cushioning responseof midsole 31, and will be discussed in terms of the configuration ofthe foam material and the hardness of the foam material. With regard tothe configuration, the foam material in midsole 31, which may have ahardness of 50-90 on the Asker C scale, for example, is concentratedadjacent edge 33 and is less prevalent in areas corresponding with thecenter of chamber 40. A change in the number of lobes 42 a-42 e may beutilized, for example, to decrease the ratio of air to foam inperipheral portions of midsole 31. This type of change in midsole 31 maybe utilized to increase the overall stiffness of midsole 31 duringcompression. Accordingly, the geometry of the foam material and thecorresponding geometry of chamber 40 have an effect upon the cushioningresponse.

Finally, the concept of film tensioning has an effect upon thecushioning response. This effect is best understood when compared topressurized prior art chambers. In the prior art chambers, the pressurewithin the chambers places the outer layers in tension. As the prior artchambers are compressed, however, the tension in the outer layers isrelieved or lessened. Accordingly, compression of the prior art chambersoperates to lessen the tension in the outer layers. In contrast with thepressurized prior art chambers, the tension in first surface 45increases in response to compression due to bending of first surface 45.This increase in tension contributes to the cushioning responsediscussed above. In applications where chamber 40 is rotated such thatsecond surface 46 is positioned adjacent the foot, the tension in secondsurface 46 will increases in response to compression, therebycontributing to the cushioning response

Pressure ramping, the properties of the foam material, and filmtensioning operate together to attenuate forces and absorb energy. Thespecific effect that pressure ramping, the properties of the foammaterial, and film tensioning has upon the cushioning response variesbased upon location with respect to chamber 40. At perimeter portions ofchamber 40, which corresponds with the locations of distal ends 43 a-43e, the properties of the foam material provides reduced compliance and,therefore, increases the corresponding stiffness. As the location tendstoward central area 41, columns 34 taper and allow a relatively largedeflection, and the dominant phenomena that attenuate forces and absorbenergy are film tensioning and pressure ramping. One skilled in therelevant art will recognize, based upon the preceding discussion, thatthe specialized cushioning response of sole structure 30 is primarilyrelated to the general configuration of chamber 40 and the foam materialof midsole 31 disclosed herein.

Based upon the considerations of pressure ramping, the properties of thefoam material, and film tensioning, the cushioning response of midsole31 is modifiable to provide a desired degree of force attenuation andenergy absorption. For example, the volume of chamber 40, the number andshape of lobes 42 a-42 e, the slope of sidewall 47, the thickness ofsurfaces 45 and 46, the material utilized to form the exterior ofchamber 40, and the position and orientation of chamber 40 withinmidsole 31 may be varied to modify the cushioning response. In addition,the properties of the foam material, including the hardness andthickness, may also be adjusted to modify the cushioning response. Byvarying these and other parameters, therefore, midsole 31 may be customtailored to a specific individual or to provide a specific cushioningresponse during compression.

Second Chamber

Another embodiment of the present invention is depicted as footwear 10′in FIG. 8. Footwear 10′ includes an upper 20′ and a sole structure 30′.Upper 20′ has a substantially conventional configuration that forms aninterior void for securely and comfortably receiving the foot. Solestructure 30′ is positioned below upper 20′ and includes two primaryelements, a midsole 31′ and an outsole 32′. Midsole 31′ is secured to alower surface of upper 20′ and operates to attenuate forces and absorbenergy as sole structure 30′ contacts the ground. Outsole 32′ is securedto a lower surface of midsole 31′ and is formed of a durable,wear-resistant material that engages the ground. In addition, solestructure 30′ may include an insole, which is a thin cushioning member,located within the void and adjacent to the foot to enhance the comfortof footwear 10′. Accordingly, footwear 10′ is generally similar instructure to footwear 10 discussed above. A primary difference offootwear 10′, however, is the structure of midsole 31′, and morespecifically the structure of a chamber 40′ that is embedded within afoam material of midsole 31′.

Midsole 31′ is primarily formed of a polymer foam material, such aspolyurethane or ethylvinylacetate, and chamber 40′ is positioned withina heel area of midsole 31′, as depicted in FIGS. 9 and 10. Chamber 40′is depicted individually in FIGS. 11-15 and includes a central area 41′,seven lobes 42 a′-42 g′, and seven corresponding distal ends 43 a′-43g′. In addition, chamber 40′ includes an axis 44′ for purposes ofreference, a first surface 45′, a second surface 46′, and a sidewall47′. Chamber 40′ is symmetrical about a plane that extends through axis44′ and is generally perpendicular to the plane of first surface 45′ andsecond surface 46′, while otherwise being asymmetrical. Whereas chamber40 has surfaces 45 and 46 with a substantially planar configuration,first surface 45′ of chamber 40′ has a curved configuration. That is,portions of first surface 45′ adjacent to distal ends 43 a′-43 c′ and 43e′-43 g′ curve upward to form a rounded or concave structure. Incontrast, the portion of first surface 45′ on lobe 42 d′ has asubstantially flat configuration.

With reference to FIGS. 9 and 10, the position of chamber 40′ in midsole31′ is depicted. In general, chamber 40′ is positioned such that secondsurface 46′ is coextensive with a lower surface of the foam material inmidsole 31′. This configuration places a portion of the foam material inmidsole 31′ between the foot and first surface 45′. Distal ends 43 a′-43c′ and 43 e′-43 g′ are also coextensive with an edge 33′ of midsole 31′.Accordingly, distal ends 43 a′-43 c′ and 43 e′-43 g′ are visible from anexterior of footwear 10′. Due to the curved configuration of secondsurface 46′, lobes 42 a′-42 c′ and 42 e′-42 g′ increase in height andvolume as they radiate outward from central area 41′ to distal ends 43a′-43 c′ and 43 e′-43 g′. The increase in volume permits a greatervolume of fluid to migrate from central area 41′ to distal ends 43 a′-43c′ and 43 e′-43 g′ during compression, thereby providing a more gradualtransition from a relatively compliant cushioning response to arelatively stiff cushioning response. Furthermore, the increase involume at the distal ends 43 a′-43 c′ and 43 e′-43 g′ reduces theoverall fluid pressure within chamber 40′ for a given degree ofcompression.

The slope of sidewall 47′, which is depicted in the cross-sectionalviews of FIGS. 13B-13D, varies around chamber 40′ to provide a smoothtransition during compression. Sidewall 47 slopes between adjacent lobes42 a′-42 g′ and has a substantially vertical slope at distal ends 43a′-43 e′. The spaces between adjacent lobes 42 a′-42 g′ have a generallyU-shaped configuration, which is created by a curved surface of sidewall47′. The portion of sidewall 47′ positioned between adjacent lobes 42a′-42 g′ has a slope that is greater in areas adjacent to distal ends 43a′-43 g′ than in areas adjacent to central area 41′. More specifically,sidewall 47′ has a relatively shallow slope adjacent to central area41′, which corresponds with the rounded portion of the U-shapedconfiguration. As sidewall 47′ extends between central area 41′ anddistal ends 43 a′-43 e′, the slope increases. At distal ends 43 a′-43e′, however, the slope of sidewall 47′ is substantially vertical.

The typical motion of the foot during running proceeds as follows:First, the heel strikes the ground, followed by the ball of the foot. Asthe heel leaves the ground, the foot rolls forward so that the toes makecontact, and finally the entire foot leaves the ground to begin anothercycle. During the time that the foot is in contact with the ground androlling forward, it also rolls from the outside or lateral side to theinside or medial side, a process called pronation. While the foot is airborne and preparing for another cycle the opposite process, calledsupination, occurs. Chamber 40 complements the motion of the foot duringrunning by providing central area 41 with greater compliance than areascorresponding with lobes 42 a-42 e, thereby resisting rolling of thefoot toward the medial side. In further embodiments, the size of lobes42 a-42 e and the properties or quantity of the foam material may bealtered to limit pronation. Similar concepts also apply to chamber 40′.

As with chamber 40, chamber 40′ and its arrangement in the foam materialof midsole 31′ produces a relatively large deflection for a given loadduring initial stages of compression when compared to the fluid-filledchambers discussed in the Background of the Invention section. As thecompression of chamber 40′ increases, however, the stiffness of chamber40′ increases in a corresponding manner due to the structure of midsole31. This effect is also the result of pressure ramping, the propertiesof the foam material in midsole 31′, and film tensioning. Accordingly,the volume of chamber 40′, the number and shape of lobes 42 a′-42 g′,the slope of sidewall 47′, the thickness of surfaces 45′ and 46′, thematerial utilized to form the exterior of chamber 40′, and the positionand orientation of chamber 40′ within midsole 31′ may be varied tomodify the cushioning response. In addition, the properties of the foammaterial, including the amount of foam material and the hardness andthickness, may also be adjusted to modify the cushioning response. Byvarying these and other parameters, therefore, midsole 31′ may be customtailored to a specific individual or to provide a specific cushioningresponse during compression.

One structural difference between chamber 40 and chamber 40′ relates tothe curved configuration of first surface 45′. With the curvedconfiguration, the effect that film tensioning has upon the cushioningresponse occurs more rapidly during compression due to the downwardangle of first surface 45′. That is, for a given degree of deflection inchamber 40′, the effect of film tensioning will have a greater effectupon the cushioning characteristics when first surface 45′ is curved.Furthermore, the curved configuration permits chamber 40′ to have afluid volume that is greater than the fluid volume of chamber 40, butwith approximately the same stiffness.

Chamber 40 and chamber 40′ were discussed in the above material toprovide examples of the many chamber configurations that fall within thescope of the present invention. In general, an chamber will have a pairof opposite surface that form lobes in the chamber. Chamber 40 andchamber 40′ were disclosed as having five and seven lobes, respectively.In other embodiments, however, the chambers may have any number of lobesranging from three to twenty, for example.

Manufacturing Method

A method of manufacturing chamber 40′ through a blow molding processwill now be discussed with reference to FIGS. 16-25. In a conventionalblow molding process for forming footwear chambers, a generally hollowand tubular structure of molten polymer material, otherwise referred toas a parison, is positioned between corresponding portions of a mold.The mold is then closed upon the parison such that a portion of themolten polymer material is drawn into the mold and conforms to the shapeof the mold. Finally, the mold compresses opposite sides of the parisontogether and forms a bond between the opposite sides. In some blowmolding process, however, an inlet remains open such that a pressurizedfluid may be injected at a later stage of the manufacturing process,with the inlet being subsequently sealed.

The conventional blow molding process described above commonly utilizesa mold having two corresponding mold portions. Each mold portion has agenerally planar surface and a recess that is formed in the surface,with the shape of the recess corresponding to one-half of the shape ofthe chamber. Accordingly, closing the mold portions forms a cavitywithin the mold with the shape of the chamber.

One consequence of the conventional mold structure is that the parisonmust stretch in order to extend into the recesses, and the stretchingdecreases the overall thickness of the parison wall. In order tocounteract the effects of stretching, the parison is generally formedwith an initial wall thickness that will stretch to the desired, lesserwall thickness. This manner of counteracting the effects of stretchingis appropriate when the mold geometry is such that the parison stretchesin a generally uniform manner. When the mold geometry is such that theblow-up ratio of some portions of the parison stretch is more than theblow-up ratio of other portions, however, merely increasing the wallthickness of the parison may not be appropriate due the resultingvariance in the wall thickness of the chamber.

Conventional mold portions with generally planar surfaces and recessesthat form a cavity with the shape of chamber 40′ would generally be ofthe type that would cause specific portions of the parison to stretchsubstantially more than other portions. For example, the portion of theparison forming the area of chamber 40′ where distal ends 43 a′-43 g′join with first surface 45′ would stretch substantially more than theportion of the parison forming central area 41′. Accordingly, thethickness of chamber 40′ at the junction of distal ends 43 a′-43 g′ andfirst surface 45′ would be substantially less than the thickness ofchamber 40′ at central area 41′. The method of manufacturing chamber40′, however, which is described below, provides a blow molding processthat forms each of first surface 45′, second surface 46′, and sidewall47′ to have a substantially uniform thickness.

Another consequence of the conventional mold structure is that a partingline is formed in a middle of a sidewall of the resulting chamber. Asdiscussed above, the mold compresses opposite sides of the parisontogether and forms a bond between the opposite sides. The bondrepresents the parting line and corresponds with the area where theopposite mold portions meet. In some footwear applications, the sidewallof the chamber is visible. A parting line positioned in a middle of thesidewall would, therefore, detract from the aesthetic properties of thechamber. The method of manufacturing chamber 40′, however, provides ablow molding process that positions the parting line away from themiddle of sidewall 47′, and particularly from areas corresponding withdistal ends 43 a′-43 g′.

A mold 100 that may be utilized to form chamber 40′ is depicted in FIGS.16-18. Mold 100 includes a first mold portion 110 and a correspondingsecond mold portion 120. When joined together, mold portions 110 and 120form a cavity having dimensions substantially equal to the exteriordimensions of chamber 40′. Unlike the conventional mold for formingfootwear chambers through a blow molding process, mold portions 110 and120 do not have generally planar surfaces adjacent to the cavity thatforms chamber 40′. Instead, first mold portion 110 defines a pluralityof indentations 111 a-c and 111 e-g, and second mold portion 120 definesa plurality of protrusions 121 a-c and 121 e-g, as depicted in FIG. 16.

First mold portion 110 is depicted individually in FIG. 17 and forms theportions of chamber 40′ corresponding with first surface 45′ and theareas of sidewall 47′ positioned adjacent to central area 41′. Firstmold portion 110 also forms that area of sidewall 47′ corresponding withdistal end 43 d′. A ridge 112 extends around a centrally-located area offirst mold portion 110. As will be discussed in greater detail below,ridge 112 is partially responsible for forming a parting line in chamber40′. Accordingly, the area of first mold portion 110 located within thearea bounded by ridge 112 forms first surface 45′ and portions ofsidewall 47′. More specifically, the surface of first mold portion 110generally located proximal to a central area 113 forms central area 41′,surfaces generally located around a plurality of lobe areas 114 a-114 gform the portions of lobes 42 a′-42 g′ on first surface 45′, andsurfaces generally located around sidewall areas 115 a-115 g form theportions of sidewall 47′ positioned adjacent to central area 41′.

The portions of first surface 45′ adjacent to distal ends 43 a′-43 c′and 43 e′-43 g′ curve upward to form a rounded or concave structure, asdiscussed with reference to chamber 40′. In order to form thisconfiguration, the area of first mold portion 110 located within thearea bounded by ridge 112 has a corresponding convex configuration.Accordingly, the surface of first mold portion 110 has a curvedconfiguration from central area 113 to sidewall areas 114 a-c and 114e-g.

An extension of ridge 112 extends outward from sidewall area 114 d andforms an L-shaped channel 116. As discussed in greater detail below,channel 116 is utilized to form a conduit through which a fluid may beinjected into chamber 40′. Another feature of first mold portion 110 isa plurality of slot vents 117 distributed throughout central area 113and sidewall areas 114 a-114 g. Slot vents 117 provide outlets for airas a parison is drawn into first mold portion 110 during the formationof chamber 40′.

Second mold portion 120 is depicted individually in FIG. 18 and formsthe portions of chamber 40′ corresponding with second surface 46′ andthe areas of sidewall 47′ corresponding with distal ends 43 a′-43 c′ and43 e′-43 g′. A ridge 122 extends around a centrally-located area ofsecond mold portion 120, and ridge 122 cooperatively forms the partingline in chamber 40′ with ridge 112. When first mold portion 110 isjoined with second mold portion 120, therefore, ridge 112 is positionedimmediately adjacent to ridge 122. The area of second mold portion 120located within the area bounded by ridge 122 forms second surface 46′and the areas of sidewall 47′ corresponding with distal ends 43 a′-43 c′and 43 e′-43 g′. More specifically, the surface of second mold portion120 generally located proximal to a central area 123 forms central area41′, surfaces generally located around a plurality of lobe areas 124a-124 g form the portions of lobes 42 a′-42 g′ on second surface 46′,and surfaces generally located around distal areas 125 a-c and 125 e-gform the portions of sidewall 47′ corresponding with distal ends 43a′-43 c′ and 43 e′-43 g′.

With reference to chamber 40′, second surface 46′ has a generally planarconfiguration. The area of second mold portion 120 corresponding withcentral area 123 and lobe areas 124 a-124 g, which forms second surface46′, also has a generally planar configuration. Distal areas 125 a-c and125 e-g extend upward from lobe areas 124 a-c and 124 e-g, respectively,to provide a generally planar area for forming distal ends 43 a′-43 c′and 43 e′-43 g′. An extension of ridge 122 extends outward from lobearea 124 d and forms an L-shaped channel 126. In combination withchannel 116, a conduit is formed through which a fluid may be injectedinto chamber 40′. Second mold portion 120 also includes a plurality ofslot vents 127, which are distributed throughout central area 123 andlobe areas 124 a-124 g. As with slot vents 117, slot vents 127 provideoutlets for air as the parison is drawn into second mold portion 120during the formation of chamber 40′.

Indentations 111 a-c and 111 e-g and protrusions 121 a-c and 121 e-gextend outward from the portions of mold portions 110 and 120 that formchamber 40′. More specifically, indentations 111 a-c and 111 e-g extendradially outward from lobe areas 114 a-c and 114 e-g, respectively.Similarly, protrusions 121 a-c and 121 e-g extend radially outward fromlobe areas 124 a-c and 124 e-g, respectively. Accordingly, indentations111 a-c and 111 e-g and protrusions 121 a-c and 121 e-g are generallyaligned with the portions of mold 100 that form lobes 42 a′-42 c′ and 42e′-42 g′.

The manner in which mold 100 is utilized to form chamber 40′ from aparison 130 will now be discussed. Parison 130 is a generally hollow andtubular structure of molten polymer material. As utilized herein, theterm tubular is not limited to a cylindrical configuration, which has acircular cross-section, but is also intended to encompass configurationshaving an elongated or oblong cross-section. In forming parison 130, themolten polymer material is extruded from a die. The wall thickness ofparison 130 may be substantially constant, or may vary around theperimeter of parison 130. Accordingly, a cross-sectional view of parison130 may exhibit areas of differing wall thickness. Suitable materialsfor parison 130 include the materials discussed above with respect tochamber 40 and chamber 40′.

Following the formation of parison 130, as described above, parison 130is suspended between mold portions. 110 and 120, as depicted in FIG. 19.For purposes of discussion, parison 130 has a first side 131 that facesfirst mold portion 110, and parison 130 has a second side 132 that facessecond mold portion 120. Mold portions 110 and 120 are then aligned suchthat indentations 111 a-c and 111 e-g correspond with protrusions 121a-c and 121 e-g, respectively. In this position, the areas of moldportions 110 and 120 that form chamber 40′ are positioned on oppositesides of parison 130 and are also aligned. Mold portions 110 and 120then translate toward each other such that mold 100 contacts parison130, as depicted in FIG. 20. More specifically, the surfaces of firstmold portion 110 in which indentations 111 a-c and 111 e-g are formedcontact first side 131, and the surfaces of second mold portion 120 thatform protrusions 121 a-c and 121 e-g contact second side 132.

When mold 100 contacts parison 130, portions of parison 130 bend toaccommodate further movement of mold portions 110 and 120 toward eachother, which is also depicted in FIG. 20. In particular, first surface131 bends into indentations 111 a-c and 111 e-g, and second surface 132bends around protrusions 121 a-c and 121 e-g. Accordingly, parison 130continues to bend as mold portions 110 and 120 continue to translatetoward each other.

Upon further movement of mold portions 110 and 120 toward each other,protrusions 121 a-c and 121 e-g extend entirely into indentations 111a-c and 111 e-g and side 131 of parison 130 is compressed against side132 of parison 130, thereby bonding portions of side 131 to side 132, asdepicted in FIG. 21. A central area of parison 130, however, contactsand conforms to the surfaces of mold 100 that are intended to formchamber 40′. Accordingly, a central area of first side 131 contacts andconforms to the contours of central area 113, lobe areas 114 a-114 g,and sidewall areas 115 a-115 g. Similarly, a central area of second side132 contacts and conforms to the contours of central area 123, areaslobe 124 a-124 g, and distal areas 125 a-c and 125 e-g. Furthermore,ridges 112 and 122 compress sides 131 and 132 together, thereby forminga bond that seals peripheral areas of chamber 40′.

As mold 100 closes, a fluid, such as air, having a positive pressure incomparison with ambient air may be injected between sides 131 and 132 toinduce parison 130 to contact and conform to the contours of moldportions 110 and 120. Initially, the fluid may be delivered from the diemechanism that forms parison 130 and may be directed along thelongitudinal length of parison 130, thereby preventing sides 131 and 132from contacting each other. Once mold 100 closes upon parison 130,however, the fluid may be directed through the conduit formed bychannels 116 and 126. For example, a needle may puncture parison 130 atthe entrance to the conduit and deliver a fluid that travels down theconduit and into the area forming chamber 40′. Air may also be removedfrom the area between parison 130 and mold portions 110 and 120 throughslot vents 117 and 127, thereby drawing parison 130 onto the surface ofmold portions 110 and 120.

Once chamber 40′ is formed within mold 100, mold portions 110 and 120separate such that the parison may be removed from mold 100, as depictedin FIGS. 23-24. The polymer material forming parison 130 is thenpermitted to cool, and the conduit formed by channels 116 and 126 may besealed to enclose the fluid within chamber 40′ at ambient pressure.Alternately, a pressurized fluid may be injected through the conduitprior to sealing. In addition, excess portions of parison 130 may betrimmed or otherwise removed from chamber 40′. The excess portions maythem be recycled or reutilized to form another parison.

Based upon the above discussion, mold portions 110 and 120 eachgenerally include a bending zone and a forming zone that have differentfunctions. With respect to first mold portion 110, the bending zoneincludes indentations 111 a-c and 111 e-g. The bending zone isresponsible, therefore, for bending parison 130 prior to bonding. Theforming zone includes central area 113, lobe areas 114 a-114 g, andsidewall areas 115 a-115 g. The forming zone is responsible, therefore,for imparting the actual shape of chamber 40′ to the parison. That is,the forming zone actually forms first surface 45′ and portions ofsidewall 47′ of chamber 40′. Similarly, bending zone of second moldportion 120 includes protrusions 121 a-c and 121 e-g and is alsoresponsible for bending parison 130 prior to bonding. The forming zoneof second mold portion 120 includes central area 123, lobe areas 124a-124 g, and distal areas 125 a-c and 125 e-g, and the forming zoneactually forms second surface 46′ and other portions of sidewall 47′.Accordingly, mold portions 110 and 120 each include a bending zone thatbends the parison and a forming zone that forms portions of chamber 47′,the bending zone being separate from the forming zone.

Sides 131 and 132 bend when mold portions 110 and 120 initially contactparison 130, as discussed above. Some portions of parison 130 maystretch, however, in order to induce parison 130 to contact and conformto the various surfaces that form chamber 40′. The purpose of bendingsides 131 and 132 when mold portions 110 and 120 initially contactparison 130 is to impart a uniformity to the stretching of parison 130.That is, the bending of parison 130 ensures that sides 131 and 132stretch in a generally uniform manner, thereby imparting a largelyuniform thickness to first surface 45′, second surface 46′, and sidewall47′ of chamber 40′.

Another advantage of bending sides 131 and 132 relates to a position ofa parting line 133, which corresponds with the area where the oppositemold portions meet adjacent to bladder 40′. That is, parting line 133 isthe bond in chamber 40′ between side 131 and side 132 that is formed byridges 112 and 122. Referring to FIG. 26, the position of parting line133 is highlighted with a dashed line for purposes of reference. In manyprior art chambers formed through a conventional blow molding process,the parting line extends horizontally across the sidewall in a linearmanner and obscures portions of the sidewall. With regard to chamber40′, however, parting line 133 does not merely extend vertically acrosssidewall 47′. Instead, parting line 133 follows a non-linear coursehaving a wave-like pattern that extends around distal ends 43 a′-43 g′.More specifically, parting line 133 extends horizontally betweensidewall 47′ and first surface 45′ at upper ends of distal ends 43 a′-43c′ and 43 e′-43 g′. Parting line 133 then extends vertically acrosssidewall 47′ and along the sides of distal ends 43 a′-43 c′ and 43 e′-43g′. Accordingly, at least a portion of parting line 133 extends betweenfirst surface 45′ and second surface 46′. Parting line 133 also extendshorizontally between sidewall 47′ and second surface 46′ in areasbetween lobes 42 a′-42 g′. When incorporated into an article offootwear, as depicted in FIG. 8, parting line 133 will generally not bevisible, and parting line 133 will not extend across distal ends 43a′-43 g′, which are the visible portions of chamber 40′. Parting line133 is, therefore, not centered in sidewall 47′.

One consequence of the non-linear parting line 133 is that specificareas of sidewall 47′ are formed from either first side 131 or secondside 132. For example, the areas of sidewall 47′ that are adjacent tocentral area 41′, which will be referred to as first areas herein, areformed by first side 131. Accordingly, the first area of sidewall 47′extends from first surface 45′ to second surface 46′ and is formed fromfirst side 131. Similarly, the areas of sidewall 47′ that form distalends 43 a′-43 c′ and 43 e′-43 g′, which will be referred to as secondareas herein, are formed from second side 132. Accordingly, the secondarea of sidewall 47′ also extends from first surface 45′ to secondsurface 46′ and is formed from second side 132. In general, the firstarea and the second area alternate such that the first side and thesecond side are interlaced to form sidewall 47′.

The blow molding method described above departs from the conventionalblow molding process for footwear chambers. For example, mold 100includes the plurality of indentations 111 a-c and 111 e-g and theplurality of protrusions 121 a-c and 121 e-g to bend parison 130 priorto bonding or stretching, thereby inducing uniformity in the wallthickness of chamber 40′. In addition, the bending of parison 130 formsa non-centered parting line 133 that does not extend across visibleportions of sidewall 47′.

Third Chamber

Another configuration of footwear 10′ is depicted in FIGS. 26 and 27 ashaving both chamber 40′ and an additional fluid-filled chamber 40″.Whereas chamber 40′ is located in the heel area of midsole 31′, chamber40″ is located in a forefoot area of midsole 31′. Accordingly, chamber40′ and chamber 40″ respectively provide force attenuation to the heeland forefoot of the wearer. Chamber 40″ is depicted individually inFIGS. 28-33 and includes a first subchamber 41 a″, a second subchamber41 b″, a third subchamber 41 c″, seven lobes 42 a″-42 g″, and sevencorresponding distal ends 43 a″-43 g″. In addition, chamber 40″ includesa pair of conduits 44 a″ and 44 b″, a first surface 45″, a secondsurface 46″, and a sidewall 47″.

Whereas chambers 40 and 40′ are suitable for use with either the leftfoot or right foot. The configuration of chamber 40″ depicted in FIGS.28-33 has an asymmetrical configuration and is most suitable for usewith the left foot, as discussed in greater detail below. Accordingly,chamber 40″ may be manufactured to have a substantially identical, butreversed, configuration that is most suitable for use with the rightfoot, as depicted in FIG. 34. Depending upon the particular style offootwear 10′ and the intended use of footwear 10′, either configurationof chamber 40″ may be utilized in footwear 10′. That is, eitherconfiguration of chamber 40″ may be utilized in footwear that isintended for either the left foot or the right foot.

Subchambers 41 a″-41 c″ form a majority of the volume of chamber 40″ andare fluidly-connected by conduits 44 a″ and 44 b″. More particularly,conduit 44 a″ extends between first subchamber 41 a″ and secondsubchamber 41 b″ to permit fluid flow between subchambers 41 a″ and 41b″. Similarly, conduit 44 b″ extends between second subchamber 41 b″ andthird subchamber 41 c″ to permit fluid flow between subchambers 41 b″and 41 c″. If first subchamber 41 a″ is compressed, the fluid withinfirst subchamber 41 a″ may pass through conduit 44 a″ and into secondsubchamber 41 b″, and a portion of the fluid within second subchamber 41b″ may pass through conduit 44 b″ and into third subchamber 41 c″. Ifthird subchamber 41 c″ is compressed, the fluid within third subchamber41 c″ may pass through conduit 44 b″ and into second subchamber 41 b″,and a portion of the fluid within second subchamber 41 b″ may passthrough conduit 44 a″ and into first subchamber 41 a″. Similarly, ifsecond subchamber 41 b″ is compressed, the fluid within secondsubchamber 41 b″ may pass through both of conduits 44 a″ and 44 b″ andinto each of subchambers 41 a″ and 41 c″. Accordingly, subchambers 41a″-41 c″ are in fluid communication with each other through conduits 44a″ and 44 b″. In some configurations of chamber 40″, valves may belocated within conduits 44 a″ and 44 b″ to limit fluid flow betweensubchambers 41 a″-41 c″, or one or both of conduits 44 a″ and 44 b″ maybe sealed to prevent fluid flow.

Subchambers 41 a″-41 c″ form each enclose a portion of the fluid withinchamber 40″. Although the relative volume of fluid within subchambers 41a″-41 c″ may vary significantly within the scope of the presentinvention, chamber 40″ is depicted as having a configuration withinfirst subchamber 41 a″ has a greater volume than both of subchambers 41b″ and 41 c″, and second subchamber 41 b″ has a greater volume thanthird subchamber 41 c″. As a comparison, first subchamber 41 a″ mayhave, for example, a volume that is approximately twice the volume ofsecond subchamber 41 b″, and second subchamber 41 b″ may have, forexample, a volume that is approximately twice the volume of thirdsubchamber 41 c″. In further configurations, chamber 40″ may exhibitsubstantially different ratios between the volumes of subchambers 41a″-41 c″. Furthermore, third subchamber 41 c″ may be significantlyreduced in size or absent from chamber 40″ in some configurations.

Subchambers 41 a″-41 c″ are arranged in a non-linear relationship,wherein second subchamber 41 b″ is located next to first subchamber 41a″, and third subchamber 41 c″ is located forward of second subchamber41 b″. More particularly, if an axis passed through each of subchambers41 a″ and 41 b″, then third subchamber 41 c″ would be spaced from thataxis. Similarly, if an axis passed through each of subchambers 41 b″ and41 c″, then first subchamber 41 a″ would be spaced from that axis. Ineffect, therefore, subchambers 41 a″-41 c″ form three points of atriangular pattern. As discussed in greater detail below, thisarrangement for subchambers 41 a″-41 c″ locates first subchamber 41 a″in a lateral portion of footwear 10′, and also locates subchambers 41 b″and 41 c″ in a medial portion of footwear 10′.

Lobes 42 a″-42 c″ extend outward from first subchamber 41 a″ and are influid communication with first subchamber 41 a″. If first subchamber 41a″ is compressed, as discussed above, a portion of the fluid withinfirst subchamber 41 a″ may also pass into lobes 42 a″-42 c″. Similarly,lobes 42 d″-42 f″ extend outward from second subchamber 41 b″ and are influid communication with second subchamber 41 b″, and lobe 42 g″ extendsoutward from third subchamber 41 c″ and is in fluid communication withthird subchamber 41 c″. In addition to passing through conduits 44 a″and 44 b″, fluid may pass into lobes 42 d″-42 g″ if either ofsubchambers 41 b″ and 41 c″ are compressed. The number and location oflobes 42 a″-42 g″ may vary significantly. In many configurations ofchamber 40″, however, each of subchambers 41 a″ and 41 b″ will generallyhave at least two of the lobes 42 a″-42 g″.

Distal ends 43 a″-43 g″ form end areas of lobes 42 d″-42 g″ and arelocated opposite subchambers 41 a″-41 c″, respectively. When chamber 40″is incorporated into footwear 10′, distal ends 43 a″-43 g″ may protrudethrough a sidewall of midsole 31′. More particularly, lobes 42 a″-42 c″may extend to a lateral side of footwear 10′ such that distal ends 43a″-43 c″ protrude through a sidewall of midsole 31′, and lobes 42 d″-42g″ may extend to an opposite medial side of footwear 10′ such thatdistal ends 43 d″-43 g″ protrude through an opposite portion of thesidewall of midsole 31′. In some configurations of footwear 10′,however, distal ends 43 a″-43 g″ may be wholly located within midsole31′, or distal ends 43 a″-43 g″ may protrude outward and beyond thesidewall of midsole 31′. In addition, distal ends 43 a″-43 g″ may beoriented substantially perpendicular to a plane on which the subchamber41 a″-41 c″.

First surface 45″ forms an upper surface of chamber 40″ and has a curvedconfiguration. That is, portions of first surface 45″ adjacent to distalends 43 a″-43 g″ curve upward to form a rounded or concave structure inthe upper area of chamber 40″. Second surface 46″ is located oppositefirst surface 45″ and has a generally planar configuration. In someconfigurations of footwear 10′, second surface 46″ may form the uppersurface of chamber 40″. In comparison with first surface 45″, secondsurface 46″ has a greater surface area. More particularly, secondsurface 46″ is depicted as having approximately twice as much surfacearea as first surface 45″, but may range from being substantially equalto having ten times as much surface area, for example. To account forthe differences in surface area, sidewall 47″ extends from a peripheryof first surface 45″ and slopes downward to a periphery of secondsurface 46″. In comparison with second surface 46″, which slopesdownward, distal ends 43 a″-43 g″ have a substantially verticalorientation.

As discussed above, the typical motion of the foot during runningincludes rolling from the outside or lateral side to the inside ormedial side, which is referred to as pronation. Chamber 40″ complementsthe motion of the foot during running through the relative locations ofthe various components of chamber 40″. First subchamber 41 a″ isgenerally located in a lateral portion of footwear 10′, and subchambers41 b″ and 41 c″ are generally located in a medial portion of footwear10′. In this configuration, at least a portion of first subchamber 41 a″and lobes 42 a″-42 c″ underlie the third, fourth, and fifthmetatarsophalangeal joints (i.e., the joints respectively between thethird, fourth, and fifth metatarsals and the third, fourth, and fifthproximal phalanges). Similarly, at least a portion of second subchamber41 b″ and lobes 42 d″-42 f″ underlie the first and secondmetatarsophalangeal joints (i.e., the joints respectively between thefirst and second metatarsals and the first and second proximalphalanges). In addition, at least a portion of third subchamber 41 c″and lobe 42 g″ underlie the first proximal phalanx and first distalphalanx (i.e., the big toe).

Based upon the positions of the various portions of chamber 40″discussed above, the foot may initially compress first subchamber 41 a″,which is located in the lateral portion of footwear 10′ during running.As first subchamber 41 a″ is compressed, the pressure of the fluidwithin first are 41 a″ increases and a portion of the fluid passesthrough conduit 44 a″ and into second subchamber 41 b″. This has theeffect of decreasing the compressibility of second subchamber 41 b″ andassists with inhibiting rolling of the foot from the lateral side to themedial side. As the foot rolls from the lateral side to the medial side,however, second subchamber 41 b″ is compressed and the fluid withinsecond subchamber 41 b″ passes through conduit 44 b″ and increases thepressure of the fluid within third subchamber 41 c″. This has the effectof decreasing the compressibility of third subchamber 41 c″ and assistswith pushing off, which occurs as the foot rolls forward and as the footis leaving the ground.

Another factor that affects the compressibility of chamber 40 and rollof the foot relates to the slope of sidewall 47″. Referring to FIGS.28-30, for example, the slope of sidewall 47″ associated with firstsubchamber 41 a″ is different in forward and rear areas. In the reararea of first subchamber 41 a″ the slope of sidewall 47″ is relativelyshallow, whereas the slope of sidewall 47″ is greater in the forwardarea of first subchamber 41 a″. The differences in slope affect thecompressibility of first subchamber 41 a″ and the degree to which thefoot rolls. More particularly, the shallower slope in the rear area offirst subchamber 41 a″ facilitates compression and roll of the foot. Asthe foot rolls forward and toward the forward area of first subchamber41 a″, the greater slope of sidewall 47″ inhibits compression of firstsubchamber 41 a″ and slows the roll of the foot. That is, areas of firstsubchamber 41 a″ with a relatively shallow slope (i.e., the rear area)are more compressible than areas of first subchamber 41 a″ with agreater slope (i.e., the forward area).

Differences in slope of sidewall 47″ are also present in secondsubchamber 41 b″ and third subchamber 41 c″. In second subchamber 41 b″,sidewall 47″ has a relatively shallow slope in areas that are adjacentto first subchamber 41 a″ and a greater slope in areas adjacent lobes 42d″-42 f″. As with first subchamber 41 a″, areas of second subchamber 41b″ with a relatively shallow slope are more compressible than areas ofsecond subchamber 41 b″ with a greater slope. This facilitates roll ofthe foot toward second subchamber 41 b″, but limits further roll of thefoot toward the medial portion of footwear 10′. Similarly, thirdsubchamber 41 c″ has a configuration wherein sidewall 47″ is relativelysteep in areas adjacent to second subchamber 41 b″, but is more shallowin forward areas of third subchamber 41 c″, thereby facilitating pushingoff.

As with chambers 40 and 40′, chamber 40″ and its arrangement in the foammaterial of midsole 31′ produces a relatively large deflection for agiven load during initial stages of compression when compared to some ofthe fluid-filled chambers discussed in the Background of the Inventionsection. As the compression of chamber 40″ increases, however, thestiffness of chamber 40″ increases in a corresponding manner due to thestructure of midsole 31′. This effect is also the result of pressureramping, the properties of the foam material in midsole 31′, and filmtensioning. Accordingly, the volume of chamber 40″, the number and shapeof lobes 42 a″-42 g″, the slope of sidewall 47″, the thickness ofsurfaces 45″ and 46″, the material utilized to form the exterior ofchamber 40″, and the position and orientation of chamber 40″ withinmidsole 31′ may be varied to modify the cushioning response. Inaddition, the properties of the foam material, including the amount offoam material and the hardness and thickness, may also be adjusted tomodify the cushioning response. By varying these and other parameters,therefore, midsole 31′ may be custom tailored to a specific individualor to provide a specific cushioning response during compression.

A variety of materials may be utilized to form chamber 40″, includingthe polymeric materials that are conventionally utilized in forming theouter layers of fluid-filled chambers for footwear, as discussed in theBackground of the Invention section. In contrast with a majority of theprior art chamber structures, however, the fluid within chamber 40″ isat ambient pressure or at a pressure that is slightly elevated fromambient. Accordingly, the pressure of the fluid within chamber 40″ mayrange from a gauge pressure of zero to over five pounds per square inch.Due to the relatively low pressure within chamber 40″, the materialsutilized to form first surface 45″, second surface 46″, and sidewall47″need not provide the barrier characteristics that operate to retainthe relatively high fluid pressures of prior art chambers. Accordingly,a wide range of polymeric materials such as thermoplastic urethane maybe utilized to form first surface 45″, second surface 46″, and sidewall47″, and a variety of fluids such as air may be utilized within chamber40″. Furthermore, the wide range of polymeric materials may be selectedbased upon the engineering properties of the material, such as thedynamic modulus and loss tangent, rather than the ability of thematerial to prevent the diffusion of the fluid contained by chamber 40″.When formed of thermoplastic polyurethane, first surface 45″, secondsurface 46″, and sidewall 47″ may have a thickness of approximately 0.04inches, but the thickness may range, for example, from 0.01 inches to0.10 inches. Depending upon the materials utilized, thicknesses les thanor exceeding this range may be utilized.

The relatively low pressure of the fluid within chamber 40″ alsoprovides another difference between chamber 40″ and prior art chambers.The relatively high pressure in prior art chambers often requires theformation of internal connections between the polymer layers to preventthe chamber from expanding, outward to a significant degree. That is,internal connections were utilized in prior art chambers to controloverall thickness of the chambers. In contrast, chamber 40″ does nothave internal connections between first surface 45″ and second surface46″.

CONCLUSION

The present invention is disclosed above and in the accompanyingdrawings with reference to a variety of embodiments. The purpose servedby the disclosure, however, is to provide an example of the variousfeatures and concepts related to the invention, not to limit the scopeof the invention. One skilled in the relevant art will recognize thatnumerous variations and modifications may be made to the embodimentsdescribed above without departing from the scope of the presentinvention, as defined by the appended claims.

1. A sealed chamber formed from a polymer material and enclosing afluid, the chamber comprising: a first subchamber having at least twooutwardly-extending first lobes, the first subchamber having a firstvolume; a second subchamber having at least two outwardly-extendingsecond lobes, the second subchamber having a second volume that is lessthan the first volume; and a third subchamber having a third volume thatis less than the second volume, each of the first subchamber, the secondsubchamber, and the third subchamber having a first surface and anopposite second surface devoid of internal connections that secureinterior portions of the first surface to interior portions of thesecond surface, and a pressure of the fluid being substantially equal toan ambient pressure of air surrounding the chamber.
 2. The sealedchamber recited in claim 1, wherein the third subchamber includes atleast one third lobe.
 3. The sealed chamber recited in claim 1, whereinan area of the first surface is less than an area of the second surface.4. The sealed chamber recited in claim 3, wherein a sloped sidewallextends between a periphery of the first surface and a periphery of thesecond surface.
 5. The sealed chamber recited in claim 1, wherein thefirst subchamber includes three first lobes and the second subchamberincludes three second lobes.
 6. The sealed chamber recited in claim 1,wherein the second subchamber is in fluid-communication with the firstsubchamber.
 7. The sealed chamber recited in claim 1, wherein distalends of the first lobes and the second lobes are oriented substantiallyperpendicular to a plane on which the first subchamber, secondsubchamber, and third subchamber lie.
 8. The sealed chamber recited inclaim 1, wherein the first surface is curved and the second surface issubstantially planar.
 9. The sealed chamber recited in claim 1, whereinthe first surface has a concave configuration.
 10. An article offootwear with an upper and a sole structure secured to the upper, thesole structure having a sealed chamber that encloses a fluid, thechamber comprising: a first subchamber located in a lateral portion ofthe footwear, the first subchamber including at least two first lobesextending outward from the first subchamber and toward a lateral side ofthe sole structure; and a second subchamber in fluid communication withthe first subchamber, the second subchamber being located in a medialportion of the footwear, and the second subchamber including at leasttwo second lobes extending outward from the second subchamber and towarda medial side of the sole structure, each of the first subchamber andthe second subchamber having a first surface and an opposite secondsurface devoid of internal connections that secure interior portions ofthe first surface to interior portions of the second surface.
 11. Thearticle of footwear recited in claim 10, wherein a volume of the firstsubchamber is greater than a volume of the second subchamber.
 12. Thearticle of footwear recited in claim 10, wherein an area of the firstsurface is less than an area of the second surface.
 13. The article offootwear recited in claim 12, wherein a sloped sidewall extends betweena periphery of the first surface and a periphery of the second surface.14. The article of footwear recited in claim 10, wherein the firstsubchamber includes three first lobes and the second subchamber includesthree second lobes.
 15. The article of footwear recited in claim 10,wherein each of the first lobes extend to the lateral side of the solestructure, and each of the second lobes extend to the medial side of thesole structure.
 16. The article of footwear recited in claim 15, whereindistal ends of the first lobes are substantially co-planar with thelateral side of the sole structure, and distal ends of the second lobesare substantially co-planar with the medial side of the sole structure.17. The article of footwear recited in claim 10, wherein the chamberincludes a third subchamber in fluid communication with the secondsubchamber, the third subchamber being located in the medial portion ofthe footwear and forward of the second subchamber.
 18. The article offootwear recited in claim 17, wherein the third subchamber includes atleast one third lobe extending outward from the third subchamber andtoward the medial side of the sole structure.
 19. The article offootwear recited in claim 17, wherein a volume of the second subchamberis greater than a volume of the third subchamber.
 20. The article offootwear recited in claim 10, wherein a pressure of the fluid issubstantially equal to an ambient pressure of air surrounding thefootwear.
 21. The article of footwear recited in claim 10, wherein thechamber is located in a forefoot region of the footwear.
 22. The articleof footwear recited in claim 10, wherein the first surface is curved andthe second surface is substantially planar.
 23. The article of footwearrecited in claim 10, wherein the first surface has a concaveconfiguration.
 24. An article of footwear with an upper and a solestructure secured to the upper, the sole structure having a sealedchamber that encloses a fluid, the chamber comprising: a firstsubchamber having at least two outwardly-extending first lobes, thefirst subchamber having a first volume; a second subchamber influid-communication with the first subchamber, the second subchamberhaving at least two outwardly-extending second lobes, and the secondsubchamber having a second volume that is less than the first volume;and a third subchamber in fluid-communication with the secondsubchamber, the third subchamber having a third volume that is less thanthe second volume, the chamber being at least partially located in aforefoot region of the footwear, each of the first subchamber, thesecond subchamber, and the third subchamber having a first surface andan opposite second surface devoid of internal connections that secureinterior portions of the first surface to interior portions of thesecond surface.
 25. The article of footwear recited in claim 24, whereinan area of the first surface is less than an area of the second surface.26. The article of footwear recited in claim 25, wherein a slopedsidewall extends between a periphery of the first surface and aperiphery of the second surface.
 27. The article of footwear recited inclaim 24, wherein each of the first lobes extend to a lateral side ofthe sole structure, and each of the second lobes extend to a medial sideof the sole structure.
 28. The article of footwear recited in claim 27,wherein distal ends of the first lobes are substantially co-planar withthe lateral side of the sole structure, and distal ends of the secondlobes are substantially co-planar with the medial side of the solestructure.
 29. The article of footwear recited in claim 24, wherein thefirst subchamber is located in a lateral portion of the sole structure,and the second subchamber and the third subchamber are located in amedial portion of the sole structure.
 30. The article of footwearrecited in claim 24, wherein a pressure of the fluid is substantiallyequal to an ambient pressure of air surrounding the footwear.
 31. Thearticle of footwear recited in claim 24, wherein the first surface iscurved and the second surface is substantially planar.
 32. The articleof footwear recited in claim 24, wherein the first surface has a concaveconfiguration.
 33. The article of footwear recited in claim 24, whereinthe third subchamber includes at least one third lobe.